CANBERRA - The Australian Greens party has criticised Papua New Guinea's plans to repatriate a "substantial number" of asylum seekers currently detained on Manus Island.

In an interview with the ABC's 7:30 program on Wednesday night, PNG Prime Minister Peter O'Neill said most of the 1,035 asylum seekers detained on Manus Island were economic migrants and would be returned to their home countries.

"I think many of them are just out there trying to have economic opportunities that Australia and other countries offer to them," Mr O'Neill said.

"We have already started talking with their representatives here in Canberra and we are asking those governments to facilitate the transfer of these people."

Mr O'Neill was asked how PNG could trust the Iranian government to truthfully assess whether an asylum seeker who had fled Iran would face persecution on his or her forced return.

"I'm hoping that we all care about our citizens and they will care about the people who are in this predicament and we will all try and do the best for these people," he said.